Biochemical Oxygen Demand or BOD, is the amount of oxygen needed by organisms to break down the organic material in wastewater. BOD in wastewater is the result of human waste, food waste and other organics which are sent to the sewers. It is normal for water to have some organics. However, the concentration in wastewater is damaging to waterways if discharged untreated, thus the need for wastewater treatment facilities. Wastewater treatment facilities have BOD discharge limits which vary by state environmental regulation and are more or less stringent, dependent on the receiving body of water.
How is BOD removed from Wastewater?
Conventional wastewater treatment facilities remove BOD using a variety of methods in primary and secondary treatment processes. In the primary treatment stage, about 30% of the BOD is removed through settling before moving on to secondary treatment. If the facility doesn’t have a Primary Clarifier then very little BOD is removed prior to secondary treatment. The organic solids removed in primary treatment are known as primary sludge and have high energy generation potential because they have not yet been broken down.
The secondary treatment stage is where the majority of the BOD is removed at a conventional wastewater treatment facility. In a facility using an activated sludge process for secondary treatment, BOD is removed through the introduction of oxygen and microorganisms which consume organic material. Secondary treatment in the form of activated sludge consumes a great deal of energy due to oxygen use and leaves behind secondary sludge with very little energy generation potential. Microorganisms have already consumed most of the readily degradable organic matter.
BOD and Anaerobic Digestion
When considering the energy generation potential from wastewater, it is important to realize that the energy comes from the organic material, or BOD. To maximize energy generation, there is a need to remove as much BOD as possible before it is broken down by the microorganisms in the secondary treatment process. By removing BOD in the primary treatment stage, the energy generation potential of organics is maximized, and the energy needed by the secondary treatment to convert BOD into organic material (with little to no energy value) is reduced.
ClearCove’s patented technology provides an enhanced primary wastewater treatment solution which removes up to 85% of the BOD before it reaches secondary treatment, resulting in greater energy generation and reduced energy consumption.